/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *  http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  package org.apache.directory.server.core.partition.impl.btree.mavibot;
  
  
  import java.io.IOException;
  
  import org.apache.directory.api.ldap.model.cursor.AbstractCursor;
  import org.apache.directory.api.ldap.model.cursor.CursorException;
  import org.apache.directory.api.ldap.model.cursor.InvalidCursorPositionException;
  import org.apache.directory.api.ldap.model.cursor.Tuple;
  import org.apache.directory.api.ldap.model.exception.LdapException;
  import org.apache.directory.mavibot.btree.TupleCursor;
  import org.apache.directory.mavibot.btree.exception.KeyNotFoundException;
  import org.apache.directory.server.i18n.I18n;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * Cursor over the Tuples of a Mavibot BTree. If the BTree allows duplicate values,
   * we will browse each value and return a Tuple for each one of them.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   */
  class MavibotCursor<K, V> extends AbstractCursor<Tuple<K, V>>
  {
      /** A dedicated log for cursors */
      private static final Logger LOG_CURSOR = LoggerFactory.getLogger( "CURSOR" );
  
      /** The table we are building a cursor over */
      private final MavibotTable<K, V> table;
  
      /** The tuple which will be returned */
      private Tuple<K, V> returnedTuple = new Tuple<>();
  
      /** A flag set when there is a Tuple available */
      private boolean valueAvailable = false;
  
      /** The Tuple browser */
      private TupleCursor<K, V> browser;
  
  
      /**
       * Creates a Cursor over the tuples of a Mavibot table.
       *
       * @param table the JDBM Table to build a Cursor over
       */
      MavibotCursor( MavibotTable<K, V> table )
      {
          LOG_CURSOR.debug( "Creating MavibotCursor {}", this );
          this.table = table;
      }
  
  
      /**
       * Cleanup the returned tuple before reusing it.
       */
      private void clearValue()
      {
          returnedTuple.setKey( null );
          returnedTuple.setValue( null );
          valueAvailable = false;
      }
  
  
      /**
       * {@inheritDoc}
       */
      public boolean available()
      {
          return valueAvailable;
      }
  
  
      /**
       * Sets the position before a given key
       * @param key The key we want to start with
       * @throws LdapException 
       * @throws CursorException
       */
      public void beforeKey( K key ) throws CursorException
      {
         checkNotClosed();
         closeBrowser( browser );
 
         try
         {
             browser = table.getBTree().browseFrom( key );
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
 
         clearValue();
     }
 
 
     /**
      * Sets the position before a given key
      * @param key The key we want to start with
      * @throws LdapException 
      * @throws CursorException
      */
     public void afterKey( K key ) throws CursorException
     {
         checkNotClosed();
 
         closeBrowser( browser );
         try
         {
             browser = table.getBTree().browseFrom( key );
 
             if ( table.isDupsEnabled() )
             {
                 browser.nextKey();
             }
             else
             {
                 if ( browser.hasNextKey() )
                 {
                     browser.nextKey();
                 }
                 else
                 {
                     browser.afterLast();
                 }
             }
 
             clearValue();
         }
         catch ( IOException e )
         {
             clearValue();
             throw new CursorException( e );
         }
     }
 
 
     /**
      * Sets the position before a given key and a given value for this key
      * @param key The key we want to start with
      * @param value The value we want to start with
      * @throws LdapException 
      * @throws CursorException
      */
     public void beforeValue( K key, V value ) throws LdapException, CursorException
     {
         throw new UnsupportedOperationException( I18n.err( I18n.ERR_596 ) );
     }
 
 
     /**
      * Sets the position after a given key and a given value for this key
      * @param key The key we want to start with
      * @param value The value we want to start with
      * @throws LdapException 
      * @throws CursorException
      */
     public void afterValue( K key, V value ) throws LdapException, CursorException
     {
         throw new UnsupportedOperationException( I18n.err( I18n.ERR_596 ) );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void before( Tuple<K, V> element ) throws LdapException, CursorException
     {
         beforeKey( element.getKey() );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void after( Tuple<K, V> element ) throws LdapException, CursorException
     {
         afterKey( element.getKey() );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void beforeFirst() throws LdapException, CursorException
     {
         checkNotClosed();
 
         try
         {
             if ( browser == null )
             {
                 browser = table.getBTree().browse();
             }
 
             browser.beforeFirst();
             clearValue();
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
         catch ( KeyNotFoundException knfe )
         {
             throw new CursorException( knfe );
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void afterLast() throws LdapException, CursorException
     {
         checkNotClosed();
 
         try
         {
             if ( browser == null )
             {
                 browser = table.getBTree().browse();
             }
 
             browser.afterLast();
             clearValue();
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
         catch ( KeyNotFoundException knfe )
         {
             throw new CursorException( knfe );
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean first() throws LdapException, CursorException
     {
         beforeFirst();
 
         return next();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean last() throws LdapException, CursorException
     {
         afterLast();
         return previous();
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean previous() throws LdapException, CursorException
     {
         checkNotClosed();
         if ( browser == null )
         {
             afterLast();
         }
 
         try
         {
             if ( browser.hasPrev() )
             {
                 org.apache.directory.mavibot.btree.Tuple<K, V> tuple = browser.prev();
 
                 returnedTuple.setKey( tuple.getKey() );
                 returnedTuple.setValue( tuple.getValue() );
                 valueAvailable = true;
                 return true;
             }
             else
             {
                 clearValue();
                 return false;
             }
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean next() throws LdapException, CursorException
     {
         checkNotClosed();
 
         if ( browser == null )
         {
             beforeFirst();
         }
 
         try
         {
             if ( browser.hasNext() )
             {
                 org.apache.directory.mavibot.btree.Tuple<K, V> tuple = browser.next();
 
                 returnedTuple.setKey( tuple.getKey() );
                 returnedTuple.setValue( tuple.getValue() );
                 valueAvailable = true;
                 return true;
             }
             else
             {
                 clearValue();
                 return false;
             }
         }
         catch ( IOException e )
         {
             throw new CursorException( e );
         }
     }
 
 
     /**
      * {@inheritDoc}
      */
     public Tuple<K, V> get() throws CursorException
     {
         checkNotClosed();
         if ( valueAvailable )
         {
             return returnedTuple;
         }
 
         throw new InvalidCursorPositionException();
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close() throws IOException
     {
         LOG_CURSOR.debug( "Closing MavibotCursor {}", this );
         super.close();
         closeBrowser( browser );
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close( Exception cause ) throws IOException
     {
         LOG_CURSOR.debug( "Closing MavibotCursor {}", this );
         super.close( cause );
         closeBrowser( browser );
     }
 
 
     /**
      * Close the browser
      */
     private void closeBrowser( TupleCursor<K, V> browser )
     {
         if ( browser != null )
         {
             browser.close();
         }
     }
 }